using two Mcintosh MC2102 in mono parallel mode

Hello,

I'm considering getting another MC2102 amp and running them in the parallel mono mode; my speakers have quite a low impedance (0.7 ohms above 6KHz). Does anyone have experience with this setup, or with another Mcintosh tube amp set up that way?

Here are some of the things I'm concerned about:

Will it work well if one amp is 4ys old and one is new?
Do the tubes on the two units need to be matched?
Does the amp input impedance change?
Does the amp sensitivity change?

Thanks for any advice on this,
-steverw